The Mexican navy says it has captured the suspected leader of the Zetas drug cartel believed to be the mastermind behind the killings discovered recently in a group of mass graves in northeastern Mexico.

The navy said Saturday it has taken Martin Omar Estrada Luna into custody in San Fernando in Tamaulipas state where the remains of at least 145 people were found in graves last week. Five other people were arrested with him.

Mexican officials say Estrada Luna, also known as "El Kilo," is also believed to be involved in the massacre of 72 Central American migrants found shot to death last year in San Fernando.

The Zetas began as a Mexican military unit that defected and began working with the Gulf cartel, based in Ciudad Juarez, Mexico, just across the border from the U.S. city of El Paso, Texas. The Zetas split from the Gulf cartel last year. The two groups are now fierce rivals.